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71 lines
2.0 KiB
Go
71 lines
2.0 KiB
Go
/*
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* Minimalist Object Storage, (C) 2015 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package pq
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import "container/heap"
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// Item container for tasks in priority queue
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type Item struct {
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task Task // task
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// The index is needed by Fix and is maintained by the heap.Interface methods.
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index int // The index of the item in the heap.
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}
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// A PriorityQueue implements heap.Interface and holds Items.
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type PriorityQueue []*Item
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// Len length of current priority queue
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func (pq PriorityQueue) Len() int { return len(pq) }
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// Less used internally by heap.Interface to arrange items in order
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func (pq PriorityQueue) Less(i, j int) bool {
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// We want Pop to give us the highest, not lowest, priority so we use greater than here.
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return pq[i].task.GetPriority() > pq[j].task.GetPriority()
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}
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// Swap used internally by heap.Interface to arrange incoming items
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func (pq PriorityQueue) Swap(i, j int) {
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pq[i], pq[j] = pq[j], pq[i]
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pq[i].index = i
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pq[j].index = j
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}
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// Push push items onto priority queue
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func (pq *PriorityQueue) Push(x interface{}) {
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n := len(*pq)
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item := x.(*Item)
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item.index = n
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*pq = append(*pq, item)
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}
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// Pop pop items with highest priority
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func (pq *PriorityQueue) Pop() interface{} {
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old := *pq
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n := len(old)
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item := old[n-1]
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item.index = -1 // for safety
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*pq = old[0 : n-1]
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return item
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}
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// Fix modifies an item in-place on the queue
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func (pq *PriorityQueue) Fix(item *Item, task Task) {
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item.task = task
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heap.Fix(pq, item.index)
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}
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